Ion-scattering spectroscopy during InGaAs molecular beam epitaxy: Reduction of sputtering using glancing-angle Ar ions

Abstract

An ion scattering spectroscopy (ISS) geometry is described that minimizes sputtering and ion damage. The key feature is the use of a glancing-incidence-angle Ar ion beam: Ar ions provide better mass resolution than He while the glancing angle minimizes sputtering. The GaAs(001) sputtering rate, measured via reflection high energy electron diffraction oscillation periods, decreased rapidly with decreasing ion impingement angle φ. For example, the sputtering rate of 3 keV Ar ions decreased from 0.122 to 0.013 ML/s (corresponding to a sputtering yield reduction for ∼3.4 to ∼0.5 atoms/ion) as φ was reduced from 15° to 3°. No sputtering was detected for E=1 keV and φ⩽9°. ISS measurements of 1-ML-thick InAs films on GaAs(001) were made using 1.1 keV Ar ions at φ=3° and a 56° scattering angle. No change in the In peak was observed after 20 min of continuous ISS scans corresponding to a dose of ∼1.6×1016 ions cm−2 (estimated yield < 0.004 atoms/ion). In segregation was observed by ISS during subsequent GaAs overlayer growth.